This invention relates to a nickel vapour deposition method of producing nickel shell molds and, more particularly, relates to a flood heating system for mandrels used in the nickel vapour deposition process.
The production of nickel molds by nickel vapour deposition is known. Nickel vapour in the form of nickel carbonyl gas is passed over a heated mandrel in a deposition chamber and, as the nickel carbonyl gas contacts the hot mandrel surface, it decomposes to form a hard and dense nickel deposit. Uniform heat transfer from the mandrel surface is required to achieve an even deposition of nickel on the surface of the mandrel.
The standard method of heating the mandrel employs hot spray jets directed at the underside of the mandrel. It has been found that the spray jet method creates hot and cold spots causing uneven heat transfer, hence uneven deposition of nickel on the upper surface of the mandrel.
U.S. Pat. No. 5,169,549 issued Dec. 8, 1992 shows a nickel shell mold formed by nickel vapour deposition onto a mandrel. The nickel shell mold is comprised of a combination steel parting line and manifold with a plurality of heating and cooling lines connected to the manifold, all of which are encapsulated within a nickel shell.